Evaluating salvage logging and forest recovery at multiple sites within the eastern deciduous forest

Background/Question/Methods

Salvage logging following windthrow is common throughout forests worldwide even though the practice is often considered inimical to forest recovery.  Because salvaging removes trees, crushes seedlings, and compacts soils, many warn this practice may delay succession, alter composition, and suppress diversity.  To date, empirical support for these concerns remains biased towards post-fire examples and is often limited by a lack of adequate control areas, low replication, and short-term evaluations.  Here, over eight years following windthrow, we experimentally evaluate the degree to which salvaging affects successional dynamics across 11 gaps wherein half of each gap was salvaged and the other left as a control.  Our gaps vary in size and we explicitly account for variation in windthrow severity and soil disturbance resulting from salvaging (i.e., scarification) so that our results would be broadly generalizable. 

 Results/Conclusions

Salvage logging had modest and ephemeral impacts on tree succession. Seedling richness and density declined over time as individuals grew into saplings and salvaging did not change these dynamics.  Salvaging initially caused a 25-38% decline in sapling abundance, richness, diversity, and non-tree vegetation cover; but these differences disappeared within five years.  Our work, coupled with an assessment of existing post-windthrow salvage studies, suggest short-term studies likely overestimate the impact of salvaging on regeneration.  Additionally, we documented interactions between windthrow severity and scarification.  Specifically, low severity windthrow and scarification combined reinforced shade-tolerant and browse-tolerant advance regeneration and decreased diversity up to 62%; although this difference also waned over time.  In contrast, severe windthrow and scarification together reduced Prunus pensylvanica density and non-tree vegetation cover by 75% and 26%, respectively and enhanced Acer rubrum and P. serotina recruitment two- and three-fold, respectively.  Thus, our findings demonstrate that salvaging creates novel microsites and mitigates competing vegetation, thereby promoting tree species coexistence and enhancing establishment of economically important hardwoods.  Our results suggest the costs and benefits of salvaging depend entirely upon the variation in canopy and soil disturbance severity as well as the timescale at which effects are evaluated.  Thus, our findings are inconsistent with the view that salvaging inexorably undermines plant diversity; rather we suggest salvaging can promote tree species coexistence.